With the strategy of service providers of telecommunications companies and the development of technology, mobile communication systems have been replaced by new ones at intervals of several years to decades to provide new services. For example, 1-G mobile communication systems from the late 1980s to the early 1990s provided services for analog mobile terminals, mainly providing voice services, which were then replaced by 2-G mobile communication systems. 2-G mobile communication systems from the mid-1990s have provided digital voice communication services such as Personal Digital Cellular (PDC), cdmaOne and Global System for Mobile Communications (GSM), and low-rate data communication services such as email services. Since the early 2000s, 3-G mobile communication services such as Wideband-Code Division Multiple Access (W-CDMA) or CDMA2000 have been widely used, providing Internet connections services via packet communications and content distribution services for distributing music, video, games, etc.
Future trends of mobile communications in Japan may involve higher-rate packet communication services provided in new communication systems including Worldwide Interoperability for Microwave Access (WiMAX), eXtended Global Platform (XGP), Long Term Evolution (LTE), and the like, high quality digital voice services in Voice over Internet Protocol (VoIP), or streaming distribution multimedia services, some of which are already available.
By providing the above services via the new communication systems, the telecommunications companies may propose new business models based on higher-rate communications and improve profitability or reduce network maintenance/management cost by introducing a system highly compatible with IP communications.
When a telecommunications company desires to provide users new services via a new communication system to increase the number of users of such services, the telecommunications company may need to continuously provide existing services via an existing system to its users while attempting to increase the number of users of the new services provided via the new communication system.
Note that there is a known technology in which amounts of radio resources to be allocated to different communication systems are optimized based on communication amounts in a target area of a base station (e.g., see Japanese Laid-Open Patent Application Publication No. 2007-529127).
In the mobile communication systems, mobile terminals of the users utilize radio waves as access lines. The communication via the radio waves may consume radio resources. That is, the radio resources that may be effectively utilized within a specific frequency range (or frequency band) are limited. For example, the frequency range suitable for the mobile communications may be specified from 100 MHz to 2.5 GHz. In practice, competing with aeronautical or maritime radio communications, the specified frequency range is not entirely used for the mobile communications. That is, the specific frequency range for the mobile communications may be divided into a number of different carrier frequency ranges for different communication systems.
Allocated with available radio frequency bands, the telecommunications companies may acquire radio resources within the allocated frequency bands to provide users various services. The amount of the radio resources may be determined based on the radio frequency bandwidth and the radio system to be used, and hence the maximum number of service recipients or the transmission rates may be determined based on the determined amount of the radio resources. When the telecommunications company utilizing an existing mobile communication system desires to introduce a new service via a new communication system, the telecommunications company may set up a new telecommunications apparatus procured from a telecommunications apparatus manufacturer to implement the new communication system. However, the telecommunications company may need to acquire available radio resources for the new service that the telecommunications company desires to provide. There may be two methods for acquiring radio resources; namely, (1) a method of allocating a new frequency band for acquiring radio resources; and 2) a method of reallocating the frequency band of the existing communication system to the new system for acquiring the radio resources.
The former method may involve a long-term deliberation for the new frequency allocation or a large investment for securing the frequencies, which may affect the business deployment of the telecommunications companies. The latter method may involve the reduction in the frequency bands already available for the existing services, which may decrease the number of users of the existing services in the existing system or the degradation of service quality.
The following describes the adverse effects that may occur if the frequency band already allocated to the existing system is reallocated to the new system for acquiring the radio resources, and how these effects may be reduced.
FIG. 1 illustrates an example of a service providing area of a mobile communication system. The telecommunications companies split the specified frequency band into plural carrier waves or carriers having specified band widths (carriers A, B, C, and D). At least one of the carriers A, B, C, and D is allocated to one service area to provide a corresponding service. The different carriers include different frequency bandwidths based on the different radio systems to which the carriers are allocated. For example, the frequency bandwidth for the cdmaOne system is set at 1.5 MHz whereas the frequency bandwidth for the W-CDMA is set at 5 MHz.
Among the recent mobile communication systems, one of the main-stream multiple access systems is code division multiple access (CDMA). In the CDMA system, multiple users share the same carrier frequency to transmit information using different codes, and each carrier may support dozens of users.
FIG. 2 illustrates an example of service providing areas of a communication system when some of the carriers allocated to the existing system are reallocated to a new system to provide a new service in the new system. In the example of FIG. 2, the carriers C and D selected from the carriers A, B, C, and D that have been allocated to the existing system are reallocated to the new system to formulate the service providing areas.
When some of the carriers allocated to the existing system are reallocated to the new system, the radio resources available for the existing system are reduced, and hence, the maximum number of users utilizing the exiting service in the target service providing area of the existing service may be reduced. For example, if 20 users are covered by one carrier, 80 users are covered by four carriers in the existing service providing area. However, after the relocating some (i.e., carriers C and D in this case) of the carriers to the new system, the existing service providing area may merely support up to 40 users, thereby imposing an adverse effect on the existing system.
In the mobile communication systems, the same mobile terminal changes its locations over time, and hence the mobile terminal preferably receives same services at different times in different areas. The coverage of the service area in the mobile communication is one of the important factors for a user to select a telecommunications company to subscribe to a mobile phone of that telecommunications company. Accordingly, when the telecommunications companies start providing services with a new system, the frequency reallocation from the existing system to the new system may be simultaneously implemented in a number of different areas to eventually acquire a wider service providing area for the new system. The acquisition of the wider service providing area may be an important factor for increasing the number of prospective users utilizing the service in the new system to make a profit.
FIG. 3 illustrates area configuration examples of plural service providing areas in which some of the carriers allocated to the existing system are reallocated to the new system to provide a new service in the new system. FIG. 3 is a conceptual diagram illustrating the service providing areas in which some of the carriers are reallocated to the new system. As illustrated in FIG. 3, due to the nature of the mobile communication systems where mobile terminals that receive the services change their locations, in some of the target areas, there is no mobile terminal that receives the service at a certain time despite the fact that the telecommunications companies are providing the services.
That is, as illustrated in FIG. 3, the carriers C and D are reallocated to the new system in an area A2; however, there is no mobile terminal that receives the service in the area A2, indicating that no communication is performed in the area A2. With this condition, if numerous users desire to have access to the services provided via the existing system in the area A2, the not currently utilized carriers C and D may further be reallocated to the existing system, thereby providing the services via the existing system. When the telecommunications company deploys the new system in the service providing area, there may be numerous mobile terminals utilizing the existing system while few mobile terminals utilizing the new system may exist in the service providing area. This may be easily expected from a situation where there are few subscribers to the new service utilizing the new system immediately after the launch of the new service.